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Originally Posted by seekn4
And there is mo proof that carcinogens cause cancer, according to all the studies we can't get away com them they r in just about everything we come in contact with, so y don't we all get cancer.
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There is proof carcinogens cause cancer. They are called carcinogens because they cause cancer. I'm having trouble accepting that someone doubts this, but if you want, just say and I can find some sources that confirm it.
To answer your question, we don't all get cancer for a couple of reasons. First, it's because your cells contain enzymes that are able to find errors in your DNA and repair them. Most problems will be fixed before they become a permanent change in your DNA. Also, the mutations needed to create cancer will need to happen in the right places. For example, cancer cells tend to have an active telomerase enzyme that repairs the ends of DNA strands when the cells replicate. Telomerase makes it so that a cell can divide indefinitely without damaging it's DNA strands in the process. Without telomerase, some of the ends of the DNA strands (the telomers) are lost with each replication. Most cells in our body don't have active telomerase, but it is possible for it to be switched on by mutations in the upstream regulatory sequences of the DNA. Such a mutation in a cell would make it many times more likely to develop into a tumor.
So essentially you could have a million mutations which do not cause cancer or you could have a few that do. Random luck plays a part. But generally, the more carcinogens you are exposed to, the more your DNA will mutate and the more mutations you accumulate, the more likely you are to have mutations in places where they could cause cancer.
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Source to back claim that radiation can cause cancer ->
Ionizing Radiation
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Originally Posted by Sample text
The hazards of exposure to ionizing radiation were recognized shortly after Roentgen’s discovery of the x-ray in 1895. Acute skin reactions were observed in many individuals working with early x-ray generators, and by 1902 the first radiation-induced cancer was reported arising in an ulcerated area of the skin. Within a few years, a large number of such skin cancers had been observed, and the first report of leukemia in five radiation workers appeared in 1911.1 Indeed, Marie Curie and her daughter Irene are both thought to have died of radiation-induced leukemia. Since that time, many experimental and epidemiologic studies have confirmed the oncogenic effects of radiation in many tissues of many species.
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Source to back claim that carcinogens cause cancer ->
The health consequences of smoking. Cancer.
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Originally Posted by Abstract
Smoking has now been identified as a definite cause of cancer at many sites (Table 2). Of all cancers in the United States, 30% could be prevented if cigarette smoking were eliminated. Organs in direct contact with smoke--the oral cavity, esophagus, lung, and bronchus--are at the greatest risk of malignancy among smokers. As many as 90% of these cancers are attributable to smoking. Organs and tissues distant from smoke are also at some increased risk. Among smokers, rates of cancer of the cervix, pancreas, bladder, kidney, stomach, and hematopoietic tissue are increased 50% to 200% over rates in nonsmokers. Risk of cancer at all sites increases with increasing exposure to cigarette smoke. Cigarette smoke contains potent carcinogens that influence carcinogenesis at both early and late stages. These carcinogens can interact with other exposures, such as alcohol, to synergistically increase the risk of cancer. The adverse carcinogenic effects of cigarette smoking, however, can be reduced for all smokers if tobacco use is stopped. The prevalence of smoking among the US population as a whole has declined from 40% in 1965 to 29% in 1987. This progress against the epidemic of tobacco use has already produced a decrease in the occurrence of the most common tumor among men, lung cancer. Unfortunately, the decline in smoking prevalence and cancer incidence has not occurred equally across US populations. Death rates of lung cancer in women continue to rise, and, based upon current smoking patterns, these rates will continue to increase into the next century. The challenge to physicians and public health workers is compelling and immediate: Abstaining from smoking is the single most effective way to reduce an individual's risk of cancer.
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There you go!